DOCSLIB.ORG

Laysan Duck (Anas Laysanensis)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Laysan Duck (Anas Laysanensis) Hawaiian Bird Conservation Action Plan Focal Species: Laysan Duck (Anas laysanensis) Synopsis: The Laysan Duck is a small, primarily nocturnal and terrestrial duck that is restricted to the small islands of Laysan and Midway. It formerly was more widespread on the larger Hawaiian Islands. The Midway population was created by translocations from Laysan in 2004 and 2005. Rising sea level, increasing storm surge, and lower precipitation associated with global climate change are expected to have serious impacts on the low-lying islands where this species occurs. Occasional outbreaks of avian botulism can cause high mortality. The primary conservation actions are preventing predators and other alien species from becoming established on these remote islands, managing habitat to provide adequate foraging and nesting sites, and establishing populations on additional islands by translocation. Male Laysan Duck, Midway. Photo Eric VanderWerf Created wetland, Midway. Photo Eric VanderWerf Geographic region: Northwestern Hawaiian Islands Group: Water birds Federal Status: Endangered State status: Endangered IUCN status: Critically Endangered Conservation score, rank: 17/20, At-risk Watch List 2007 Score: Red Laysan Ducks feeding on brine flies around the hypersaline Climate Change Vulnerability: High lake on Laysan. Photo Cameron Rutt Population Size and Trend: On Laysan, the most recent (2010) population estimate was 434±72 birds (Reynolds et al. 2011), but estimates have fluctuated from 322-688 over the last several decades (USFWS 2004). The population trend on Laysan is thought to be stable, but it has been difficult to determine due to the fluctuations. On Midway, 42 birds were translocated in two cohorts from Laysan in 2004 and 2005. The population on Midway increased rapidly to 473 (95% CI 439–508) in 2010 (Reynolds et al. 2012), though it has declined to around 300 after botulism outbreaks and the 2011 Japan tsunami (USFWS unpubl. data). Laysan Ducks have been kept in captivity since 1957, but most captive birds are not considered useful for reintroduction purposes because of concerns about the spread of disease and genetic introgression from hybridization with other waterfowl species in captivity (Reynolds and Kozar 2000). Range: The Laysan Duck currently is found only on Laysan Island and Midway Atoll, which are located in the Northwestern Hawaiian Islands (NWHI). The ducks use most of each island, Laysan Duck profile - 1 October 2012 Hawaiian Bird Conservation Action Plan but both islands are very small; Laysan is 414 hectares (1,023 acres) in size, and Midway encompasses 596 hectares (1,473 acres; Krause et al. 2012). Even with the establishment of a second population on Midway, the Laysan Duck is thought to have the smallest range of any waterfowl species in the world, less than 10 km2. Laysan Ducks were still extant on Lisianski, also in the NWHI, as late as 1844 (Olson and Ziegler 1995). Fossil and subfossil evidence indicates that Laysan Ducks were widespread in the Hawaiian Islands prior to the arrival of rats (Rattus spp.) and occurred on Hawai‘i, Moloka‘i, O‘ahu, Maui, and Kaua‘i (USFWS 2004). Essential Biology: The Laysan Duck is a small (420-500 g) brownish duck wing orange legs and a white patch around the eye. The bill is greenish in males and orange in females. The amount of white on the head increases with age (Moulton and Marshall 1996). Laysan Ducks are unusual among waterfowl in being largely nocturnal and terrestrial. They forage primarily at night and rarely fly, preferring to walk. They exhibit several adaptations to a largely terrestrial lifestyle, including longer legs, shorter wings, fewer primary feathers, and reduced flight muscles (Moulton and Marshall 1996). Because they nest on the ground and tend to freeze rather than flush, Laysan Ducks are vulnerable to predation by mammals and today occur only on predator- free islands. The habitat requirements of the Laysan Duck include dense vegetated cover for nesting, a year-round prey base, and a source of fresh water (USFWS 2004). They use all available habitats on Laysan and Midway, including upland vegetation, ephemeral wetlands, freshwater seeps, mudflats, the hypersaline lake, and coastal areas. Laysan Ducks feed on terrestrial and wetland invertebrates, algae, and seeds (USFWS 2004). Historical and paleoecological evidence suggests this species was a habitat generalist and occurred in a wide range of habitats. On high elevation islands, Laysan Ducks once were found in both coastal wetland and upland forests. The clutch size is small for a duck, averaging 3.8 eggs (Moulton and Marshall 1996). The chicks are precocial and can walk and swim almost immediately after hatching, but they follow the female to learn how and where to feed. Ducklings have more restrictive habitat requirements than adults because of their higher nutritional needs for growth and initial inability to process salt water. Duckling activities therefore are concentrated around sources of fresh water with nearby cover and high prey densities. The female provides almost all parental care, but breeding pairs exhibit long-term pair bonds (Reynolds et al. 2009). Laysan Ducks molt all of their flight feathers simultaneously, usually in July-August, causing them to become flightless Laysan Duck profile - 2 October 2012 Hawaiian Bird Conservation Action Plan for several weeks until the new feathers have grown in, during which time they are even more vulnerable to predation. Annual adult survival is high; survival of released birds on Midway was 0.65±0.08 (Reynolds et al. 2012), but juvenile survival is low (10-30%; USFWS 2002). Primary Threats: Small population size and range. Small populations with limited ranges are especially vulnerable to a variety of natural processes. Fluctuations in demographic parameters such as survival and reproduction can cause population declines and even extinction. The Laysan Duck’s limited range exacerbates the risk of extinction due to catastrophes such as droughts, tsunamis, severe storms, and disease epizootics. Loss of genetic variation is more likely in small populations, potentially limiting adaptation to changing conditions, although there is no evidence of inbreeding depression in Laysan Ducks so far. Habitat loss and degradation. On Laysan, filling of the hypersaline lake by invasive wetland plants and declining precipitation during drought are concerns given the importance of the lake as foraging habitat. On Midway, some of the freshwater wetlands created for ducks were inundated with salt water and physically damaged by the Japan tsunami in March 2011. Most of these wetlands have recovered to near pre-tsunami levels after being pumped and salinity is steadily dropping. These wetlands continue to be vulnerable to saltwater incursions from high wave events and rising sea level, requiring periodic maintenance including removal of alien mosquito fish (Gambusia affinis) and preventing algae and plants from filling the wetlands. Non-native predators. Laysan Ducks disappeared from the main Hawaiian Islands 800– 900 years ago after rats were introduced. Laysan and Midway, where the Laysan Duck is currently found, are free of non-native mammalian predators but accidental introduction of predators to Midway and Laysan is a potential threat. However, the long-term recovery strategy for the species calls for re-establishment of populations on the larger, high-elevation Hawaiian Islands, all of which are inhabited by a variety of non-native predators. Establishment of such populations will require protecting them from predators including feral dogs (Canis familiaris), feral cats (Felis silvestris), small Indian mongooses (Herpestes auropunctatus), rats (Rattus spp.), Cattle Egrets (Bulbulcus ibis), Barn Owls (Tyto alba), and bullfrogs (Rana catesbeiana). These predators are pervasive throughout the islands, but mongooses are not established on Kauai, Kahoolawe, or Niihau. Non-native invasive plants. Several species of invasive alien plants can alter habitat structure and decrease its value for Laysan Ducks. On Laysan, the non-native grass Cenchrus echinatus is highly invasive and can crowd out the native bunch grass Eragrostis variabilis, which is the preferred nesting substrate for Laysan Ducks. Eradication of this invasive grass was expensive and required 10 years of year-round effort. Pluchea indica is a wetland invasive shrub that degrades foraging habitat on Laysan and accelerates wetland filling. Avian diseases. Avian botulism has occurred in Laysan Ducks on Midway and a severe outbreak in August 2008 caused the death of 181 ducks (Work et al. 2010). Botulism is a paralytic disease caused by ingestion of a toxin produced by the bacterium Clostridium botulinum, which thrives under anaerobic conditions in warm water with decomposing vegetation and animal carcasses. Birds can be treated and vaccinated if detected early. Removing carcasses of dead birds helps to reduce the severity of the outbreak. Wetland Laysan Duck profile - 3 October 2012 Hawaiian Bird Conservation Action Plan exclusion and water control structures have been proposed as additional methods of reducing the impact of outbreaks and possibly controlling the environmental conditions that can foster botulism. Mortality has been documented on Laysan due to drought, emaciation, and infestation by the nematode Echinurea uncinata (Work et al. 2004). Global climate change. Climate change and associated sea-level rise caused by thermal expansion of ocean water and melting of ice sheets is a serious
Load more

Recommended publications
  • The Endemic Ducks of Remote Islands DAVID LACK Introduction with the Names and Measurements of the Resident Forms of Anas
    Ducks of remote islands 5 The endemic ducks of remote islands DAVID LACK Introduction with the names and measurements of the resident forms of Anas. On large islands This paper is concerned with all those and on islands near continents many ducks which have formed distinctive sub­ species of ducks coexist. For instance, 13 species restricted to one particular small species, 7 in the genus Anas, breed regu­ and remote island or archipelago. Only larly in Britain (Parslow 1967), 16 species, dabbling ducks in the genus Anas are 6 in the genus Anas, in Iceland (F. involved. Many species in this genus have Gudmundsson pers, com.), 8, 5 in the an extremely wide range, but the average genus Anas, in the Falkland Islands number of subspecies per species is as (Cawkell and Hamilton 1961) and 7, with low as 1.9 for the 38 species recognised 2 more in the nineteenth century, 4 in the by Delacour (1954-64). Hence the fact genus Anas, in New Zealand (Williams that nearly all the ducks on remote small 1964). Some of the Falklands and New islands are separate subspecies means that, Zealand forms are endemic, not so those for ducks, they belong to relatively of British or Iceland. Although the isolated populations. In contrast, on some various species of ducks look superficially of the archipelagos concerned, notably alike, especially when seen together in a the Hawaiian Islands and Galapagos, collection of living waterfowl, they have various of the land birds are distinctive in fact evolved an adaptive radiation species or even genera.
    [Show full text]
  • A 2010 Supplement to Ducks, Geese, and Swans of the World
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Ducks, Geese, and Swans of the World by Paul A. Johnsgard Papers in the Biological Sciences 2010 The World’s Waterfowl in the 21st Century: A 2010 Supplement to Ducks, Geese, and Swans of the World Paul A. Johnsgard University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/biosciducksgeeseswans Part of the Ornithology Commons Johnsgard, Paul A., "The World’s Waterfowl in the 21st Century: A 2010 Supplement to Ducks, Geese, and Swans of the World" (2010). Ducks, Geese, and Swans of the World by Paul A. Johnsgard. 20. https://digitalcommons.unl.edu/biosciducksgeeseswans/20 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Ducks, Geese, and Swans of the World by Paul A. Johnsgard by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. The World’s Waterfowl in the 21st Century: A 200 Supplement to Ducks, Geese, and Swans of the World Paul A. Johnsgard Pages xvii–xxiii: recent taxonomic changes, I have revised sev- Introduction to the Family Anatidae eral of the range maps to conform with more current information. For these updates I have Since the 978 publication of my Ducks, Geese relied largely on Kear (2005). and Swans of the World hundreds if not thou- Other important waterfowl books published sands of publications on the Anatidae have since 978 and covering the entire waterfowl appeared, making a comprehensive literature family include an identification guide to the supplement and text updating impossible.
    [Show full text]
  • Effectiveness of Social Stimuli in Attracting Laysan Albatross to New Potential Nesting Sites
    EFFECTIVENESS OF SOCIAL STIMULI IN ATTRACTING LAYSAN ALBATROSS TO NEW POTENTIAL NESTING SITES RICHARD H. PODOLSKY • Universityof Michigan,School of Natural Resources,Ann Arbor,Michigan 48109 USA Al•sTRACT.--Seabirdcolonies usually grow as first-time breeders join existing groups. I testedthe hypothesisthat the presenceof conspecifics,specifically the sight and sound of establishedbreeders, was the stimulus responsiblefor first-time breeders to join existing colonies.The attractivepower of conspecificswas testedby presentingto conspecificsmodels of LaysanAlbatross (Diomedea immutabilis) in severalbehavior postures, with accompanying recordings of vocalizations. I found that Laysan Albatross landed more frequently in areas where both albatrossmodels and vocalizationswere present than in areaswith only visual stimuli or no vocal stimuli. Landing albatrossand those on the ground were found nearer to the artificial social stimuli than would be expectedfrom a random distribution. Three- dimensionalmodels were more attractivethan two-dimensionalmodels, and paired models were more attractive than single models for both three-dimensionaland two-dimensional models.Three-dimensional models in a sky-pointingposture were the mostattractive overall, whereas models in head-forward posture were the most attractive two-dimensional models. Albatrossexhibited courtshipbehavior closerto the modelsthan would be expectedfrom a random distribution. The implicationsof attraction to endangeredbird managementand restorationare discussed.Received 3 April 1989,accepted
    [Show full text]
  • MILLERBIRD Acrocephalus Familiaris Native Resident, Endemic, Endangered A.F
    MILLERBIRD Acrocephalus familiaris native resident, endemic, endangered A.f. familiaris (Laysan) Laysan subspecies extinct A.f. kingi (Nihoa) The Millerbird is an endemic resident in the Northwestern Hawaiian Islands (AOU 1998), having likely colonized the archipelago from Asia or other Pacific Island groups (Bryan 1940; Berger 1972, 1981; E 31:47). Acrocephalus warblers have widely colonized the Pacific Basin (Pratt et al. 1987, Wiles 2005, Cibois et al. 2011), and Millerbird has been found to be genetically distant from other Pacific congeners (AOU 1983, Fleischer et al. 2007), being the first to diverge from other taxa within a Polynesian clade (Cibois et al. 2011). Cassin (1858) followed by Dole (1869, 1879) reported an Acrocephalus warbler (as "Tatare otaiensis") in the marshes of Kaua'i and Hawai'i, which caused Rothschild (1900) and Bryan (1901a) to consider it a possibility on these islands, but Cassin was apparently referring to Acrocephalus caffer which is not found in Hawaii (see Tahiti Reed Warbler). No subfossil evidence exists for the occurrence of Acrocephalus in the Southeastern Hawaiian Islands (Olson and Ziegler 1995), which is curious given the genus' widespread distribution within the Pacific Basin (Bryan 1940). Two subspecies of Millerbird have been found, on Laysan and Nihoa, which are distinct and could be treated as different species (Wetmore 1924, Munro 1944, Olson and Ziegler 1995, Olson 1996b, Fleischer et al. 2007) but most regard them as subspecies (see Synonymies). See Banko (1979) for locations of 104 specimens of Millerbird, and Morin et al. (1997) for a summary of the natural history and biology of the species.
    [Show full text]
  • Albatross Or Mōlī (Phoebastria Immutabilis) Black-Footed Albatross Or Ka’Upu (Phoebastria Nigripes) Short-Tailed Albatross (Phoebastria Albatrus)
    Hawaiian Bird Conservation Action Plan Focal Species: Laysan Albatross or Mōlī (Phoebastria immutabilis) Black-footed Albatross or Ka’upu (Phoebastria nigripes) Short-tailed Albatross (Phoebastria albatrus) Synopsis: These three North Pacific albatrosses are demographically similar, share vast oceanic ranges, and face similar threats. Laysan and Black-footed Albatrosses nest primarily in the Northwestern Hawaiian Islands, while the Short-tailed Albatross nests mainly on islands near Japan but forages extensively in U.S. waters. The Short-tailed Albatross was once thought to be extinct but its population has been growing steadily since it was rediscovered in 1951 and now numbers over 3,000 birds. The Laysan is the most numerous albatross species in the world with a population over 1.5 million, but its trend has been hard to determine because of fluctuations in number of breeding pairs. The Black-footed Albatross is one-tenth as numerous as the Laysan and its trend also has been difficult to determine. Fisheries bycatch caused unsustainable mortality of adults in all three species but has been greatly reduced in the past 10-20 years. Climate change and sea level rise are perhaps the greatest long-term threat to Laysan and Black-footed Albatrosses because their largest colonies are on low-lying atolls. Protecting and creating colonies on higher islands and managing non-native predators and human conflicts may become keys to their survival. Laysan, Black-footed, and Short-tailed Albatrosses (left to right), Midway. Photos Eric VanderWerf Status
    [Show full text]
  • THE HAWAIIAN-EMPEROR VOLCANIC CHAIN Part I Geologic Evolution
    VOLCANISM IN HAWAII Chapter 1 - .-............,. THE HAWAIIAN-EMPEROR VOLCANIC CHAIN Part I Geologic Evolution By David A. Clague and G. Brent Dalrymple ABSTRACT chain, the near-fixity of the hot spot, the chemistry and timing of The Hawaiian-Emperor volcanic chain stretches nearly the eruptions from individual volcanoes, and the detailed geom­ 6,000 km across the North Pacific Ocean and consists of at least etry of volcanism. None of the geophysical hypotheses pro­ t 07 individual volcanoes with a total volume of about 1 million posed to date are fully satisfactory. However, the existence of km3• The chain is age progressive with still-active volcanoes at the Hawaiian ewell suggests that hot spots are indeed hot. In the southeast end and 80-75-Ma volcanoes at the northwest addition, both geophysical and geochemical hypotheses suggest end. The bend between the Hawaiian and .Emperor Chains that primitive undegassed mantle material ascends beneath reflects a major change in Pacific plate motion at 43.1 ± 1.4 Ma Hawaii. Petrologic models suggest that this primitive material and probably was caused by collision of the Indian subcontinent reacts with the ocean lithosphere to produce the compositional into Eurasia and the resulting reorganization of oceanic spread­ range of Hawaiian lava. ing centers and initiation of subduction zones in the western Pacific. The volcanoes of the chain were erupted onto the floor of the Pacific Ocean without regard for the age or preexisting INTRODUCTION structure of the ocean crust. Hawaiian volcanoes erupt lava of distinct chemical com­ The Hawaiian Islands; the seamounts, hanks, and islands of positions during four major stages in their evolution and the Hawaiian Ridge; and the chain of Emperor Seamounts form an growth.
    [Show full text]
  • Annual Weather/Climate Data Summary 2010 Pacific Island Network
    National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Annual Weather/Climate Data Summary 2010 Pacific Island Network Natural Resource Data Series NPS/PACN/NRDS—2012/273 ON THE COVER Sunset at American Memorial Park (AMME), Saipan, Commonwealth of the Northern Mariana Islands. Photograph courtesy of National Park Service staff. Annual Weather/Climate Data Summary 2010 Pacific Island Network Natural Resource Data Series NPS/PACN/NRDS—2012/273 Tonnie L. C. Casey National Park Service Inventory and Monitoring P.O. Box 52 Hawaii National Park, HI 96718 April 2012 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado publishes a range of reports that address natural resource topics of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Data Series is intended for the timely release of basic data sets and data summaries. Care has been taken to assure accuracy of raw data values, but a thorough analysis and interpretation of the data has not been completed. Consequently, the initial analyses of data in this report are provisional and subject to change. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. Data in this report were collected and analyzed using methods based on established, peer- reviewed protocols and were analyzed and interpreted within the guidelines of the protocols.
    [Show full text]
  • Notes on the Birds Peculiar to Laysan Island, Hawaiian Group
    3S4 V'lS,•ER,Birds of La),san Island. FL AukOct. NOTES ON THE BIRDS PECULIAR TO LAYSAN ISLAND, HAWAIIAN GROUP. 1 BY WALTER K. FISHER. •ølates x_,r_,r-x WE DOnot naturally associateland birds with tiny coral atolls in tropicalseas. It is thereforea strangefact that sucha diminu- tive island as Laysan, and one so remote from continentalshores, should harbor no less than five peculiar species: the Laysan Finch (]klespiza cantans) and Honey-eater (I-Iima•ione freethi), both • drepanidid' birds, the Miller Bird (.4crocefihalusfamiliaris), the LaysanRail (?orzanulapalmeri),and lastly the LaysanTeal (•tnas laysanensis).I usethe term ' land birds' loosely,in con- tradistinctionto sea-fowl,multitudes of which breed here through- out the year. The presenceof these speciesis all the more remarkablebecause none appear on neighboringislands, more or less distant, someof which are very similar to Laysan in structure and flora. Reachingout towardJapan from the main Hawaiian group is a long chainof volcanicrocks, atolls,sand-bars• and sunkenreefs, all insignificantin size and widely separated. The last islet is fully two thousandmiles from Honolulu and about half-way to Yokohama. Beginningat the east,the more importantmembers of this chain are: Bird Island and Necker (tall volcanicrocks), French Frigate Shoals, Gardner Rock, Laysan, Lisiansky, Mid- way, Cure, and Motell. Laysanis eighthundred miles northwest- by-westfrom Honolulu,and is perhapsbest knownas beingthe home of countless albatrosses. We sightedthe island early one morning in May, lying low on the horizon,with a great cloud of sea-birdshovering over it. On all sides the air was lively with terns, albatrosses,and boobies, •These notes were made during a visit of the Fish Commissionsteamer ' Albatross' to Laysan, May 17 to 23, 19o2, and are abridged from a more extendedreport on the avifauna of the i•land• to appearin the Bulletin of the U.S.
    [Show full text]
  • Handbook of Waterfowl Behavior: Tribe Anatini (Surface-Feeding Ducks)
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Handbook of Waterfowl Behavior, by Paul Johnsgard Papers in the Biological Sciences January 1965 Handbook of Waterfowl Behavior: Tribe Anatini (Surface-feeding Ducks) Paul A. Johnsgard University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/bioscihandwaterfowl Part of the Ornithology Commons Johnsgard, Paul A., "Handbook of Waterfowl Behavior: Tribe Anatini (Surface-feeding Ducks)" (1965). Handbook of Waterfowl Behavior, by Paul Johnsgard. 16. https://digitalcommons.unl.edu/bioscihandwaterfowl/16 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Handbook of Waterfowl Behavior, by Paul Johnsgard by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Subfamily Anatinae 125 Aix. During extreme excitement the male will often roll his head on his back, or even bathe. I have not observed Preening-behind-the- wing, but W. von de Wall (pers. comm.) has observed a male per- form it toward a female. Finally, Wing-flapping appears to be used as a display by males, and it is especially conspicuous because each sequence of it is ended by a rapid stretching of both wings over the back in a posture that makes visible the white axillary feathers, which contrast sharply with the black underwing surface. Copulatory behavior. Precopulatory behavior consists of the male swimming up to the female, his neck stretched and his crest de- pressed, and making occasional Bill-dipping movements. He then suddenly begins to perform more vigorous Head-dipping movements, and the female, if receptive, performs similar Bill-dipping or Head- dipping movements.
    [Show full text]
  • Genetic Divergence Among Populations of the Hawaiian Duck, Laysan Duck, and Mallard
    The Auk 110(1):49-56, 1993 GENETIC DIVERGENCE AMONG POPULATIONS OF THE HAWAIIAN DUCK, LAYSAN DUCK, AND MALLARD ROBERT A. BROWNE,• CURTICE R. GRIFFIN, 2 PAUL R. CHANG, 2 MARK HUBLEY, • AND AMY E. MARTIN s •Departmentof Biology,Wake Forest University, Winston-Salem, North Carolina27109, USA; and 2Departmentof Forestryand Wildlife Management, University of Massachusetts,Amherst, Massachusetts 01003, USA ABSTRACr.--Allozymicvariation at 20 gene loci was estimatedfor populationsof the Laysan Duck (Anaslaysanensis) and the Hawaiian Duck (A. wyvilliana)from the Hawaiianarchipelago, as well as for Mallard populations(A. platyrhynchos)from Hawaii and North America. The Laysan Duck and Hawaiian Duck are endemic, have experiencedsevere bottlenecks,and are listed as endangered species.Alternative alleles are fixed at six loci for Mallards versus Hawaiian anatids (Hawaiian and Laysan ducks). In contrast,every allelic variant found in the Laysan Duck was present in the Hawaiian Duck (but not vice versa), suggestingthe formeris an offshootof the latter.The geneticdistance (Nei's D) betweenLaysan and Hawaiian ducks is lessthan 0.01, while that between both Hawaiian and Laysan ducks and Mallards is greater than 0.45. The allozymic evidence also suggeststhat there has been extensive hy- bridization between Mallards and Hawaiian Ducks on Oahu, with the near disappearanceof Hawaiian Duck alleles.However, there is only slight evidenceof Mallard genic introgression into the Hawaiian Duck population on Kauai. Finally, the allozymic data suggestthat the Hawaiian Duck is a distinctspecies from the Mallard, but that little geneticdivergence has occurredbetween Hawaiian and Laysanducks. Received 25 July 1991,accepted 8 March 1992. THERESULTS of evolutionary processeson oce- and maintenance of populations of Hawaiian anic islands are evident in the Hawaiian avi- Ducks on Oahu and Hawaii relied on progeny fauna, which exhibits striking examples of from relatively few captive-reared birds.
    [Show full text]
  • THE FORAGING ECOLOGY, HABITAT USE, and POPULATION DYNAMICS of the LAYSAN TEAL (Anas Laysanensis)
    THE FORAGING ECOLOGY, HABITAT USE, AND POPULATION DYNAMICS OF THE LAYSAN TEAL (Anas laysanensis) by Michelle H. Reynolds A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology Virginia Polytechnic Institute and State University Approved by Jeffery R. Walters, Committee chair Curtis Adkisson, Committee member E. F. Benfield, Committee member James Fraser, Committee member William Steiner, Committee member Defense date October 31, 2002 Blacksburg, VA Keywords: Anas laysanensis, foraging ecology, habitat use, population estimate, survival, island waterfowl, Laysan Island THE FORAGING ECOLOGY, HABITAT USE, AND POPULATION DYNAMICS OF THE LAYSAN TEAL (Anas laysanensis) Michelle H. Reynolds ABSTRACT The Laysan teal, an endangered species, is restricted to a single population on Laysan Island, a remote atoll of the Hawaiian archipelago. Little is known of the Laysan teal’s ecology, therefore, I examined food habits, habitat use, and population dynamics. These aspects of its ecology are fundamental to the species management and conservation. I described diel and nocturnal habitat use, home range, and foraging with radio telemetry in 1998-2000. Most individuals showed strong site fidelity during the tracking period, but habitat selection varied between individuals. Mean home range size was 9.78 ha (SE 2.6) using the fixed kernel estimator (95% kernel; 15 birds with >25 locations). Foraging was strongly influenced by time of day: birds spent only 4% of their time foraging in the day, but spent 45% of their time foraging at night. Time activity budgets from the island’s four habitat zones indicated that the coastal zone was rarely used for foraging.
    [Show full text]
  • Northwestern Hawaiian Islands/Kure Atoll Assessment and Monitoring Program
    Northwestern Hawaiian Islands/Kure Atoll Assessment and Monitoring Program Final Report March 2002 Grant Number NA070A0457 William j. Walsh1, Ryan Okano2, Robert Nishimoto1, Brent Carman1. 1 Division of Aquatic Resources 1151 Punchbowl Street Rm. 330 Honolulu, HI 96813 2 Botany Department University of Hawai`i Mānoa Honolulu, HI 96822 2 INTRODUCTION The Northwest Hawaiian Islands (NWHI) consist of 9,124 km2 of land and approximately 13,000 km2 of coral reef habitat. They comprise 70% of all coral reef areas under U.S. jurisdiction. This isolated archipelago of small islands, atolls, reefs and banks represent a unique and largely pristine coral reef ecosystem. The islands support millions of nesting seabirds and are breeding grounds for the critically endangered Hawaiian monk seal and threatened green sea turtle. The reefs include a wide range of habitats and support a diverse assemblage of indigenous and endemic reef species, many of which have yet to be described. Kure Atoll, located at the northwestern end of the NWHI chain (approximately 28º 25’ N latitude and 178º 20’ W longitude) is the northernmost atoll in the world. The atoll is located 91 km northwest of Midway Islands and nearly 1,958 km northwest of Honolulu. It is a nearly circular atoll with a diameter of 10 km (6mi). The outer reef is continuous Figure 1. IKONOS satellite image of Kure Atoll 3 and almost encircles the atoll’s lagoon except for passages to the southwest (Fig. 1). An emergent rock ledge consisting primarily of coralline algae and algally bound and encrusted coral is present along some sections of the reef crest.
    [Show full text]